27. The interest rate that doubles a sum in 10 years is
a) 12%
b) 11%
c) 10%
d) 9%

Interest rate of 7%.

Step-by-step explanation:

The compound interest formula is given by:

Where A(t) is the amount of money after t years, P is the principal(the initial sum of money), r is the interest rate(as a decimal value), n is the number of times that interest is compounded per year and t is the time in years for which the money is invested or borrowed.

In this question:

We want to find t for which when . So

So a interest rate of 7%.

30.5*10=350$

you have to multiply the number without the decimal point then add it later but if its tenn u must move the place value of the decimal point 1 to the right.